blood direct renin activity level serum renin activity level serum direct renin activity level 2014-06-25T12:39:56Z CMO:0002501 JSmith Measurement of the amount of renin activity in a specified sample of serum (the clear liquid that separates from blood after it has clotted completely, i.e. blood plasma from which fibrinogen has been removed) via the direct immunologic detection of the renin protein in the sample and subsequent conversion of the protein level to an activity level. clinical_measurement_ontology